- Author: Ben Faber
Several calls have come in from growers lately about yellow avocado and citrus trees. the yellowing is most common on the late summer flush leaves or can affect the whole canopy on young trees. In severe cases leaves fall. This happens going into winter after a warm fall when growing conditions are good. During the winter, the root systems become depleted of stored starch and die.
During winter, trees go into what is called a “quiescent” state, a version of dormancy found in subtropical tree crops. This is a resting mode that protects them to a certain degree from frost damage. There is not much that can be done in a field setting until temperatures warm up and the trees begin growing again in late winter/early spring. As the temperatures increase, the trees gradually recover and the foliage re-greens.
Winter Yellows can be exacerbated in years when we do not have leaching rains to remove salts from the root zone. And it can also be more severe when we have those years when winter rains just never seem to stop and rootzones become waterlogged. We may never see that time again.
Photo by Greg Moulds
- Author: Ben Faber
I am amazed how such a simple procedure can go so wrong. For avocado and citrus growers, it’s time to think about planting in the spring. And every spring and summer I get called out to diagnose trees that are failing. It often turns out that the trees have been planted too deeply. There are various ways of killing a tree, such as digging a hole too deeply and then backfilling. When the ground settles, it settles around the root collar and the tree suffocates. Or installing a dry root ball and then not irrigating soon enough. Or adding fertilizer to the planting hole which burns the roots. One of the major problems of lack education and supervision of the planting crew. Don’t assume that everyone knows how to plant a tree.
Deep planting can result in death of woody plants either because they rot in moisture saturated soils or they dry out. In either case, the symptoms are similar: wilting, sunscald or burnt leaves, lack of growth, leaf drop and eventual death of leaves, shoots and branches. Root balls planted below grade cause several problems at establishment. Since native soil surrounds the ball, there is an immediate problem with and interface between the two soil textures. Most container media are lighter than bulk soil, which is done to make sure there is adequate drainage in the nurse. When these soil-free media are planted in soil which is of a heavier texture, the interface does not allow the water to enter the root ball.
When trees are planted too deeply, they are much more subject to fungal cankers and other pathogens that can girdle the stem, killing it and all above ground parts. Planting slightly higher than grade will prevent this. Just look for the color, textural change between the roots and stem and dig the hole no deeper than the root ball to prevent settling. Newly planted trees can’t draw water from bulk soil, not until the roots move out into the soil will they be able to absorb water. Also planting cannot be rushed, because that’s when errors in planting occur.
- Author: Ben Faber
USDA Creates Multi-Agency Emergency Response Framework to Combat Devastating Citrus Disease | |||||
USDA Providing $1 million to Jump Start Citrus Response Framework | |||||
WASHINGTON, December 12, 2013 - The U.S. Department of Agriculture today announced the creation of a new, unified emergency response framework to address Huanglongbing (HLB), a serious disease of citrus that affects several U.S. states and territories. This new framework will allow USDA and its many partners to better coordinate HLB resources, share information and develop operational strategies to maximize effectiveness. "USDA listened to the citrus industry's request for more urgency and greater coordination on the response to HLB and is implementing an emergency response structure," said Secretary Tom Vilsack. "To jump start this initiative and affirm our commitment to industry, USDA is also providing $1 million to be used in support of research projects that can bring practical and short-term solutions to the growers in their efforts to combat this disease. Through the Specialty Crop Research Initiative of the Farm Bill, USDA has provided $9 million in research to blocking the ability of insects to spread HLB to healthy trees. We need Congress to quickly pass a new Farm, Food, and Jobs Bill that continues to support this kind of research to protect a crop worth more than $3 billion in the last harvest." The new framework will bring together USDA's Animal and Plant Health Inspection Service (APHIS), Agricultural Research Service (ARS) and National Institute of Food and Agriculture (NIFA), along with state departments of agriculture and the citrus industry into a Multi-Agency Coordination (MAC) Group for HLB. It will provide industry with a single contact for all the federal and state entities that work on citrus issues and better enable the collective to collaborate on policy decisions, establish priorities, allocate critical resources, and collect, analyze, and disseminate information. The HLB MAC Group will also help coordinate Federal research with industry's efforts to complement and fill research gaps, reduce unnecessary duplication, speed progress and more quickly provide practical tools for citrus growers to use. HLB, also known as citrus greening, is named for the green, misshapen, and bitter-tasting fruit it causes. While this bacterial disease poses no danger to humans or animals, it has devastated millions of acres of citrus crops throughout the United States and abroad. In the United States, the entire States of Florida and Georgia are under quarantine for HLB, and portions of California, Louisiana, South Carolina and Texas are also under quarantine for the disease. The U.S. Territories of Puerto Rico and the U.S. Virgin Islands are under HLB quarantines as well. You can find more information about HLB and the HLB MAC Group on USDA's Multi-Agency Response to Devastating Citrus Disease website. See the USDA Animal and Health Inspection Service's website for additional Q&A Contact: # Note to Reporters: USDA news releases, program announcements and media advisories are available on the Internet and through Really Simple Syndication (RSS) feeds. Go to the APHIS news release page at www.aphis.usda.gov/newsroom and click on the RSS feed link. USDA is an equal opportunity provider and employer. To file a complaint of discrimination, write: USDA, Office of the Assistant Secretary for Civil Rights, Office of Adjudication, 1400 Independence Ave., SW, Washington, DC 20250-9410 or call (866) 632-9992 (Toll-free Customer Service), (800) 877-8339 (Local or Federal relay), (866) 377-8642 (Relay voice users). |
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- Author: Ben Faber
We have had resurgence of broad mite damage on coastal lemons this year. We haven't seen damage like this in a long time. Chlorpyriphos should care of it, but with small orchards, spray drift can be an issue. We looked at releasing the predatoiry mite Neoseiulus californicus. In the lab we challenged broad mite successfully so we took it out to the field. This is not the best time to release, because of the cold weather. Also it's best to release into a rising pest pressure. When there are too many pest mites, it's difficult to get good control. We released at an economic level of about 100 per tree, whihch would cost about $150 per acre. We've counted for 5 weeks and there is little apparent control in the field. ikt's just been too cold to build the population of beneficials. We'll try again next spring if the broad miter is there.
Curlling leaves from mite damage and the small mites hiding in fruit depressions
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Evaluating Damage to Baby Trees Requires Patience
Earlier temperatures and forecasted temperatures do not appear to be cold enough to freeze baby trees in the citrus belt. Time will tell. Semi-dormant wood in the winter looks dry even when it is healthy, so any final evaluation should be conducted in the warmth of spring. With warmer temperatures, frozen bark will peel easily from the young trunk and the degree of damage easily estimated. A tree, even those frozen down to the top of the wrap, can make an amazing recovery. Growers, in the summer after the 1990 freeze had some success budding onto the rootstocks that remained after the scions were killed by frost.
It may be better to replace a tree if it is still alive under the trunk wrap but badly damaged. Badly frozen trees regrow fairly slowly, and often are not able to resist pathogens that grow into the wood such as fungal Fusarium species causing dry root rot. Slow growing Fusarium in the wood can take up to 10 or 15 years to kill a tree.
Badly Frozen Young Trees
Badly frozen fruit may start dropping from the tree shortly after the freeze, but other fruit may hang on the tree longer than unfrozen fruit. Many growers resist picking or dropping frozen fruit in that it is another expense, at a time of little income. Reasons for dropping the fruit, even if it cannot be sold for juice, include:
Ensuring that the frozen fruit does not interfere with spring fruit set. Navel oranges, for example, will not set as much fruit if last season’s fruit remains on the tree.
Old frost-damaged fruit may harbor fungal pathogens that may infect the new crop, such as clear rot (Penicillium sp.), tear staining (Colletotrichum sp), brown rot (Phytophthora sps.) or Septoria organisms.
Avoiding having to separate last year’s partially frozen fruit from the new crop at harvest next year.
Preventing partially frozen fruit from providing habitat for insect pests.